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Terms in this set (154)
to cause disease
What are the 5 steps required for pathogenesis?
3. avoid/overcome host defenses
4. damage to tissues
What is the movement of the pathogen from its reservoir to an infected host?
What is a reservoir?
where a pathogen survives and multiplies until it can enter a new host
What are some types of reservoirs?
-environment (soil, water)
During transmission, _________ humans show no signs of disease, while _______ humans do show signs of disease
What is the difference between signs and symptoms?
-signs: things other people can see (Externally) such as fever or sweating
-symptoms: things other people can't see (pain)
Provide examples of diseases that use humans only as reservoirs
Why will pathogens use humans as reservoirs?
-sensitive to environmental change
-only attach to human tissues
use animal reservoirs (primary site of survival and multiplication is in animals)
T/F: zoonotic pathogens live solely in animals
false! can also live in humans
Provide examples of diseases that use animals as reservoirs
What are examples of diseases caused by a pathogen found in soil (environmental reservoir)?
Tetanus- Clostridium tetani
Diarrhea-= Bacillus cereus
What are examples of diseases caused by a pathogen found in water (environmental reservoir)
Cholera- Vibrio cholerae
Typhoid fever- Salmonella typhi
When water is an environmental reservoir for a pathogen, what is normally the cause?
the water is fecaly-contaminated
What are some factors that influence transmission of a disease?
- # of microbes
-source of microbe
-portal of entry
-microbial genetic factors
What is the portal of entry?
opening in body that determines which cell receptors the microbe may be exposed to (openings and surfaces that have contact with the environment)
What are some portals of entry (specifically)?
nose, ears, sinuses, mouth, anus, urethra, vagina, eyes, skin
What are the 3 main portals of entry?
1. skin (External surface)
2. mucous membrane (internal)
3. parenteral route (break in skin or mucous membrane... like a cut or tear)
Describe horizontal transmission
(what we normally think of... person--> person from the reservoir (human, animal, or environment) to a new host
What is vertical transmission?
generational (mother--> children)
When can vertical transmission occur?
1. in utero
2. during birth
What are the 3 types of horizontal transmission?
1. contact transmission
2. common vehicle transmission
3. vector transmission
_________ transmission can occur directly, indirectly, or through droplets
Direct contact transmission can occur through
-parenteral route (shared needles, blood transfusions, injuries)
What are some examples of direct contact-caused disease?
boils & impetigo (staph infections)
Indirect contact transmission can occur through _____, which are what?
-nonliving intermediate that carries the pathogen to new host
Kleenex, the desk top, and a doorknob are all examples of _____
_____ transmission can occur waterborne, food-borne, or airborne
Waterborne vehicle transmission occurs when food or water is contaminated with _____ material. This is common in underdeveloped countries and in daycares.
Describe food-borne vehicle transmission.
-pathogen contaminates uncooked or improperly cooked foods
Describe air-borne vehicle transmission
- pathogen resists drying and temp changes
-travels >1 meter
What is the most contagious and dangerous vehicle transmission?
Provide examples of diseases caused by air-borne pathogens
1. Mycobacterium tuberculosis (TB)
2. Bordetella pertusis (whopping cough)
3. Measles virus
What are the 2 forms of vector transmission?
Mechanical vector transmission does what?
carries pathogen on/in body
What are examples of mechanical vectors?
In _______ vector transmission, the pathogen lives and is replicated in arthropod (Coincidental)
Examples of biological vectors
-blood sucking arthropods like:
(femal Anopheles mosquito...we used DDT to wipe them out in the US)
During development, the pathogen must cross ______
Examples of vertically transmitted diseases caused during development
syphilis, Foxoplasmosa (Associated with cats)
Describe how pathogens are spread in vertical transmission during birth
child encounters pathogen while passing through the vagina
Examples of vertically transmitted diseases caused during birth
N. gonorrhea and Chlamydia trachomatis and HIV
How does a child acquire a disease from his/her mother after birth?
he/she receives pathogen through breast milk
Examples of vertically transmitted diseases caused after birth
Why is attachment required for a microbe to cause a disease?
the host's nonspecific defenses routinely removes unattached microbes
What are some examples of things the body does to prevent attachment of microbes?
ciliary escalator, saliva, urination
How specific is attachment?
is usually species-specific, but is also often tissue specific
(Microbe/host) are the external proteins, glycoproteins, or carbohydrates
(Microbe/host) are the membrane proteins or glycoproteins
________ have an adhesin, while ______ have a receptor
What is adhesin?
the sticky stuff on the outside of the microbe
What are receptors?
things that have a normal function... the microbe has complementary structure that enables attachment
T/F: microbes change adhesins
True! this can occur as infection goes on
Adhesins are often associated with bacterial ____
What are some examples of microbes and hosts attaching?
M and F proteins from Streptococcus progenies attaching to host cell Fibronectin receptors
an antibody-generating substance (normally a protein or carb on the outside of the microbe)
What are examples of antigens?
spike proteins on the outside of Influenza A envelope
What is the "hiding" strategy microbes use to overcome host defenses?
concealment of antigen
What do intracellular pathogens do?
avoid circulating antibodies and cytotoxic T cells
T/F: Only some viruses are intracellular pathogens
false. ALL are
Intracellular bacteria can be obligate or facultative. What is the difference?
facultative= can live inside host cell, but doesn't have to replicate there
Examples of obligate intracellular bacteria
Chlamydia, Rickettsia, Mycoplasma
Examples of facultative intracellular bacteria
Mycobacterium, Yersinia (the plague)
What are examples of protozoa that are intracellular pathogens?
Sporozoans, like Plasmodium (causes malaria)
How does the "hiding" strategy in microbes work?
hide antigens so the immune system doesn't respond
What are the 3 ways intracellular bacteria and protozoa can hide to overcome host defenses?
1. survive phagolysosome degradation by inhibiting phagolysosome formation
2. Escape degradation by destroying phagolysosome membrane
3. Induce phagocytosis by non-leukocytes
Example of pathogen that can survive phagolysosome degradation by inhibiting phagolysosome formation
Example of pathogen that can escape degradation by destroying phagolysosome membrane
Example of pathogens that can induce phagocytosis by non-leukocytes
Salmonella and Shigella
What is a leukocyte? What does it do?
-white blood cell
-designed to engulf bacteria/foreign microbes
-sends out pseudopods to engulf & form phagosome
-phagosome fuses w/ lysosome---> phagolysosome
-attaches to epithelial ell and injects it w/ proteins to rearrange the cytoskeletal elements so it can engulf bacteria
In the "hiding strategy," ___________ are locations that don't normally contain circulating antibodies or Cytotoxic T cells
Where are privileged sites?
-cerebral spinal fluid (CSF)
-synovial joints & testes
Epithelial layers privileged sites
CSF layers privileged sites
To conceal antigens (hide), the pathogen can be coated with __________ molecules to prevent detection by immune defenses. An example is ________, which binds plasma proteins to membrane
What avoid/overcome host defense strategy is this: change in protein structure of primary antigens used by immune system to destroy pathogen
antigen variation (DISGUISING)
During antigenic variation, there is a change to he antigen that is produced by _______ or _________
mutation or recombination
What is a mutation?
change in genetic info so that the key antigens aren't recognized by the immune system
What are two examples of mutations that arise and lead to antigenic variation?
HIV (1 million x more mutation than any other pathogen)
Influenza A is an example of antigenic drift (a part of antigenic variation). What does this mean?
It is a slow accumulation of mutations in the key antigens as the virus spreads through the population. It allows the virus to reinfect the original person after sufficient drift
_________ is the exchange of genetic info from 2 different sources
What is an example of recombination (a part of antigenic variation)?
Influenza A (recomb. btw swine/bird influenza A virus and human influenza A virus causes a pandemic)
What is programmed gene switching?
A programmed rearrangement of genetic info to alter the key antigens that the immune system is targeting
What is an example of programmed gene switching?
Trypanosoma (causes African sleeping sickness and CHagas disease)
What is the destruction or inhibition of components of the immune system which enable the microbial pathogen to survive until it spreads to a new host?
As a part of immunosuppression, what is an example of a virus that inhibits humoral/cell-mediated immune systems
HIV: it destroys T4 lymphocytes (they control maturation of cell-med/humoral immune systems)
As a part of immunosuppression, what is an example of a virus that destroys T cells
As a part of immunosuppression, what is an example of a virus that destroys B cells
EB virus (mononucleosis)
As a part of immunosuppression, what is an example of a protein that destroys antibodies
IgA protease produced by meningitis-causing bacteria
Inhibition of humoral & cell-mediated immune systems, destruction of T cells, B cells, or antibodies, and inhibition of phagocyte functions are all ways host defenses can be overcome/avoided as part of _________
See notes about antigenic drift example
Influenza A- Billy/girl/farmer example
What are the 3 ways damage can be done to a host? (general/broad)
1. direct damage
2. indirect damage
What are the forms of direct damage?
1. cell lysis
2. tissue damage
What are the forms of indirect damage?
-exotoxins (neurotoxins, enterotoxins, cytotoxins)
What is cell lysis?
pathogen affects individual cells and host cell explodes
Cell lysis is a form of _____ damage
Cell lysis includes all lytic ______ and _______ bacteria
Rhinovirus and Rotavirus are examples of what type of damage?
direct damage...specifically, cell lysis
Chlamydia and Rickettsia are examples of what type of damage?
direct damage...specifically, intracellular bacteria
What kind of damage involves destroying sheets of cells ?
tissue damage (a type of direct damage)
Shigella is an example of what type of damage?
direct damage...specifically, tissue damage (destroys layers of intestinal epithelium)
Describe how shigella is an example of tissue damage.
pathogen moves from lumen--> basement membrane so cell layer is "popped" off
What is indirect damage?
when a microbe itself doesn't cause damage, but something the microbe PRODUCES does
What are the 2 main forms of indirect damage?
enzymes & toxins
Hemolysin is one enzyme that causes indirect damage. What does it do?
Leukocidin is one enzyme that causes indirect damage. What does it do?
kills WBC (leuko= white, cidin= kill_
Hyaluronidase and Collgenase are two enzymes that cause indirect damage. What do they do?
cause flesh-eating diseases
-Hyaluronidase: found in cartilage
-Collagenase: found in connective tissue
DNAse is one enzyme that causes indirect damage. What does it do?
Streptokinase is one enzyme that causes indirect damage. What does it do?
dissolves blood clots
Coagulase is one enzyme that causes indirect damage. What does it do?
causes blood clots
Which 2 enzymes that cause indirect damage are opposites?
streptokinase and coagulase
Phospholipase is one enzyme that causes indirect damage. What does it do?
digests phospholipids to destroy cell membrane
T/F: bacteria produce only 1 enzyme
false: some can produce more than one
What are the common enzyme-damaging pathogens?
Staphylococcus and Streptococcus
What is the other form of indirect damage besides enzymes?
What are toxins?
What are the 2 types of toxins?
-endotoxins & exotoxins
(endo/exo)toxins are made by all gram - bacteria, while (endo/exo)toxins are made by some gram + and - bacteria
How do toxins cause indirect damage to host cell?
alter physiology of certain tissues
There is only one kind of (endotoxin/exotoxin)
There are over 200 different kinds of (endotoxin/exotoxin)
(endotoxin/exotoxin)s contain lipid A of the outer membrane
(endotoxin/exotoxin)s contain proteins
(endotoxin/exotoxin)s always have the same effect because of their chemical makeup
(endotoxin/exotoxin)s have different effects because there are different structures
Describe the process of how endotoxins cause indirect damage to host cells.
1. gram - cell is phagocytized by leukocyte
2. digested inside phagolysosome
3. bacteria is chewed up and Lipid A is released
4. Lipid A stimulates production & release of Interleukin-1 and Tumor Necrosis Factor
What is IL-1?
interleukin-1: produced and released by Lipid A (endotoxin). It resets the thermostat in hypothalamus to higher temps--> fever
What is TNF?
tumor necrosis factor: produced and released by Lipid A (endotoxin). Multiple pathways can damage capillaries to cause fluid loss and disseminated coagulation (multiple clots forming all over)
Explain how fevers relate to endotoxins.
Lipid A produces & releases Interleukin-1 which resets your thermostat to higher temperature and causes fever. Then, the growth rate is slowed down and the leukocytes work better
Why can endoxtoxins be lethal (hint: there are 3 ways)?
2. disseminated intravascular coagulation
3. acute respiratory distress syndrome
Describe shock as a result of endotoxins' lethality.
massive fluid loss--> heart failure
Describe DIC as a result of endotoxins' lethality.
(disseminated intravascular coagulation): multiple organ failure from damage to multiple capillary beds clotting
Describe ARDS as a result of endotoxins' lethality.
(Acute respiratory distress syndrome): fluid loss in lungs blocks gas exchange
What are the subunits of exotoxins?
______ binds to specific cell type, while ______ changes the physiology of the cell (subunits of exotoxins)
What are the types of exotoxins?
Where do neurotoxins target?
where do enterotoxins target?
Where do cytotoxins target?
whatever cell they bind to will die
The types of exotoxins are classified based on their _______
What is the example of a neurotoxin (type of exotoxin)?
Botulism (Clostridium botulinium)
Describe how the botulism toxin works
-produces 2 subunit toxin & 1 binds to motor neuron
-prevents vesicles from docking w/membrane
-inhibits release of acetylcholine from motor end plates
-no muscle fiber depolarization
-flaccid paralysis (death b/c you can't inhale)
What is botulism used for? Why does this work?
botox injections... inactivates neuromuscular junction for 6 months
Clostridium botulinium is a neurotoxin. It is gram (+/-) and forms ______
Endospores are found in what food/food product?
What is an example of an enterotoxin?
Cholera toxin (Vibrio cholerae)
Describe how the cholera toxin works
-binds to lg intestine epithelium
-activates adenylate cyclase (synthesizes cAMP)
-->cAMP alters membrane permeability to reverse osmotic gradient
-water is drawn out of intestinal epithelium
-die from rapid dehydration (lg intestine pumps water out instead of in)
Vibrio cholerae is gram (+/-)
Vibrio cholerae has 2 subunits: A and B. What is the function of A?
increases adenylate cyclase to increase cAMP activity
-reverses Na/K pumps (huge [solute] outside) so more water is pumped out via osmosis (DIARRHEA)
What is an example of a cytotoxin?
Describe how the dypyheria toxin works.
-receptor targets pharynx and heart
-toxin binds to elongation factor and inhibits protein synthesis
---> die from nectoric tissue in pharynx dislodging and blocking glottal opening OR
---> die from heart failure
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